WHAT IS SYNARTHROSIS? CHARACTERISTICS AND TYPES - MEDICINE - 2025

Synarthrosis is a concept used to refer to joints that have little or no movement, that is, bones that are interconnected, but cannot move in any direction.

Synarthrosis can occur in the skeletal system by the union of bones through fibrous connective tissue, or by the fixation of one bone in another that functions as a receptor cavity.

Its function is associated with offering protection and support. There are several cases of synarthrosis, one of them is represented by the skull bones; also found on the face and long growing bones.

Features of synarthrosis

Synarthrosis is a normal physiological condition; Its most outstanding characteristic is that the joint cavity and synovial capsule are not present, as is the case in other joints in which mobility is generated.

There are cases in which synarthrosis occurs due to genetic failures, in anatomical parts where it should not exist, generating a pathology.

In the case of growing bones, the synarthrosis joint is present while they are developing. Once growth is complete, the bones join through ossification of the tissue and synostosis occurs.

Classification of non-mobile joints or synarthrosis

Depending on the structure of the joints of the bones, synarthrosis can be classified into:

Suture

Called suture symphibrosis, referred to the union of the bones by a dense fibrous connective tissue. They present various forms of union:

• Serrata suture symphibrosis: it receives this name given that the union of the bones is presented in an irregular way, fitting together in the form of a “saw”. An example of this: the fronto-parietal union.
• Squamous suture symphibrosis - Two bones are joined via beveled edges. Example: parietal-temporal union.
• Harmonic suture symphibrosis: they present flat edges at the junction of the bones. Example: the naso-nasal junction.
• Schindilesis suture symphibrosis: it results from the joint in which a thin plate of bone is embedded in a cleft formed by two other nearby bones. Example: the sphenoid rostrum and the perpendicular ethmoid plate with the vomer.

Syndesmosis

In this type of synarthrosis, a less dense fibrous connective tissue is present than in that of the suture, allowing only a very slight mobility between the bones. This slight mobility should not be confused with the diarthrosic or amphiarthrosic types of joints.

This type of synarthrosis is observed in the union of bones that are separated from each other, being then united by a membrane interposed between both bones, called the interosseous membrane. Example: the tibiofibular joint.

Gonphosis

It results from the enclave of one bone within another, as in a kind of peg. Such is the case of the teeth on the alveolar edges of the jaw.

Synchondrosis

In this case of synarthrosis, the typical union of bones with fibrous tissue does not exist; the union of bone and cartilage occurs. An example of this are the chondrocostal joints.

Synostosis

The bones are fused with each other, generally occur in the growing bones,

References

1. University of Navarra Clinic (2015). Medical Dictionary: Synarthrosis. Recovered from cun.es.
2. Monserrat Abbey Library. (2010). Complete course in human anatomy. P. 35
3. IMAIOS. E-anatomy: Anatomical structures. Recovered from imaios.com
4. Georgia Highlands College. Biology: Articulations. Recovered from highlands.edu.
5. Mc Graw Hill Education. Anatomy Phisiology: The unity of form and function. Recovered from palmbeachstate.edu.